The Egyptian police has orders to arrest 300 leaders and members of Mohamed Morsi's Muslim Brotherhood after the army deposed the Islamist president on Wednesday, the website of the official Al-Ahram newspaper reported early Thursday.
A senior interior ministry official confirmed to AFP that arrest warrants had been issued for "Muslim Brotherhood members", but provided no further details.
Morsi's whereabouts, meanwhile, remained unknown.
A presidential aide said that Morsi had been moved from his office at the headquarters of the Republican Guards to an undisclosed location.
Several of his aides said they had lost all communication with Morsi and do not know what his status is.
The interior ministry official, a police general, confirmed police arrested Saad al-Katatni, who heads Morsi's Freedom and Justice Party, and Rashad Bayoumi, the deputy Supreme Guide of its mother organisation the Muslim Brotherhood.
The Freedom and Justice Party said on its Facebook page that security men in plainclothes arrived at Katatni's house and took him to an undisclosed location.
Other senior leaders of the Islamist movement have switched off their phones.
The police general added that security forces arrested workers in "unlicenced television stations," referring to Islamist channels taken off the air on Wednesday.